As the developments of electric vehicles and potable electronic devices such as mobile phones, digital cameras, and laptops, the market for lithium ion batteries with high efficiency and high energy density increasingly grow. Lithium ion battery has the highest voltage and highest energy density in commercial batteries, and has good prospects for development. However, as more and more lithium ion batteries are used in electric vehicles, hybrid vehicles, wireless power tools, and military, the voltage and energy density of the lithium ion battery have higher requirements.
A lithium ion battery is composed by electrodes, separator, and electrolyte. The stability of the electrolyte is an important component in lithium ion batteries, to ensure the stable performance of the lithium ion battery. The electrochemical window of a conventional electrolyte used in the lithium ion battery only reaches about 4.5V, that is, a charging voltage higher than 4.5V causes an oxidation decomposition of the electrolyte, making the electrolyte difficult to use at higher voltages.
In prior art, there are numerous studies on adding additives in the electrolyte to improve the functions and performances. However, the conventional additives are for improving the cycling performances at high voltages and capacity retentions of the lithium ion batteries. It has not been found a report to expand the electrochemical window of the electrolyte by adding the additives.